Mobile wireless communications subscriber devices and cellular subscriber communications networks are increasingly providing and supporting technologies that enable and exploit the location of the subscriber devices, for example, for compliance with the emergency location services, like E-911 mandated by the Federal Communications Commission, and increasingly for location-based e-commerce services and applications.
Some satellite positioning system (SPS) enabled subscriber devices compute position at the subscriber device. In some instances the subscriber device computes location autonomously. In communications networks, however, many subscriber devices require assistance information from the network for accurate location computation. This information may include, for example, precise time, frequency calibration, and satellite positioning system navigation information, etc. Other SPS enabled subscriber devices provide information, for example, pseudorange measurements, to the network, which computes the position of the subscriber device.
Other location technologies also rely on information provided by the subscriber device. MS-assisted Enhanced Observed Time Difference (E-OTD) location technologies, for example, rely upon timing measurements made by subscriber devices. In the case of MS-assisted E-OTD technology, some subscriber devices perform neighbor cell measurements in anticipation of E-OTD location requests by the network.
Many communications networks however do not support location technologies, and some networks support one technology but not others. Thus many subscriber devices may perform location measurements or computations that are not required by a particular network, resulting in unnecessary power consumption and less than optimal resource allocation. Anticipatory E-OTD measurements taken in idle mode/standby or camped state will, for example, increase current drain, which reduces battery life. Some subscriber device E-OTD software may reduce battery life by as much as 5 or 10 percent, depending, for example, on the frequency with which the subscriber device makes E-OTD measurements, among other factors.
Global System for Mobile Communications (GSM) 04.31, Radio Resource Location Services Protocol (RRLP) specifies the location technology supported by networks in a location request message. Under this standard, however, a subscriber device does not know what location technology is supported by the network until a location request is received by the subscriber device from the network. Meanwhile, the subscriber device may make power consuming location measurements that are unsupported or not required by the network.
GSM 04.35, Broadcast Network Assistance For E-OTD and Global Positioning System (GPS) Methods specifies the broadcast of E-OTD and GPS Assistance Data in an SMS Cell Broadcast (SMSBC) message. The E-OTD Assistance data includes base station coordinate information, and the GPS assistance data includes GPS Differential Correction data for computing location at the subscriber device using E-OTD and GPS technologies, respectively.
In some subscriber devices, location measurements made at the subscriber device may affect its operation. In some devices, for example, anticipatory E-OTD measurements require resources that would otherwise be allocated for dedicated modes of operation, resulting in the degradation of adjacent channel scanning and searching performance.
The various aspects, features and advantages of the present inventions will become more fully apparent to those having ordinary skill in the art upon careful consideration of the following Detailed Description of the Invention with the accompanying drawings described below.